The present invention relates to an apparatus for connecting tubular members and a method for achieving the same. In particular, the present invention relates to an apparatus and method for connecting tubular members of use, for example, in oil field applications.
In many operations the need arises to connect tubular members, such as pipes for carrying fluids. This is particularly the case in oil field operations, especially in offshore operations for the exploration or production of hydrocarbons. One particular need for means to connect tubular members arises during offshore operations when it is desired to connect a riser from the surface structure or vessel to a wellhead located on the sea floor. The development of deep draft caisson vessels (DDCV) and tension leg platforms (TLP) has led to a need for the subsea wellhead installations and the riser systems to be of a compact design, in order to reduce weight, and space and loading requirements. A number of designs of connectors for use in oilfield applications have been proposed, details of which are as follows.
U.S. Pat. No. 3,322,443 discloses a quick coupling device for tubular bodies comprising a male member having a pin portion and a female member having a socket for receiving the pin portion of the male member. A nut is threaded onto the outer portion of the pin portion of the male member and carries on its outer surface a series of cams. The cams on the outer surface of the nut cooperate with corresponding cams on the inner surface of the socket portion of the female member when the pin portion is inserted into the socket. Rotation of the nut brings the cams on its outer surface into engagement with the cams on the inner surface of the socket, the action of which is to urge the male and female members towards each other in the axial direction. This connector requires special members to be formed on both of the tubular bodies to be joined in order to provide the male and female members. Such a connector could not be used to join existing, standard members, such as risers and wellheads.
U.S. Pat. No. 3,986,729 discloses a connecting apparatus for releasably connecting with the end of a tubular member. The connector comprises a connector body having a seating surface for engaging with a complementary seating surface on the tubular member. The connector further comprises a discontinuous locking ring having a conical locking surface. The locking ring is expandable and contractible in a circumferential direction, allowing it to be moved into and out of engagement with a locking shoulder on the tubular member. In a one embodiment, the locking ring is carried by the connector body for engagement with a locking shoulder disposed on the outer surface of the tubular member. In a second, alternative embodiment, the locking ring is carried so as to be engagable by radially outwards movement with a locking shoulder disposed within the tubular member.
A pipe coupling is disclosed in U.S. Pat. No. 3,997,199 mountable on the external surface of a pipe. The coupling comprises a tapered compression ring and a split ring slip having a taper cooperating with that on the compression ring. A set screw is used to cause the split ring slip to move in an axial direction, the taper on the ring slip acting to urge the compression ring against the outer surface of a pipe place in the coupling. The pipe coupling of U.S. Pat. No. 3,997,199 is secured, for example by welding, to the outside of the pipes being coupled, thereby leading to a significant increase in the diameter of the pipe assembly in the region of the coupling.
U.S. Pat. No. 4,049,297 discloses a pipe coupling apparatus also employing a series of tapered slips or collets. In the device of U.S. Pat. No. 4,049,297, a first elongated housing encloses tapered slips or collets, which work against a tapered portion of the inner surface of the first housing. Hydraulic pressure is used to drive a piston to slide the collets against the taper of the housing, in turn forcing the collets against the outer surface of a first pipe. A second housing encloses the end portion of a second pipe. A piston is disposed within the second housing in connection with a hydraulic system. The piston has a tapered portion, which, under the action of the hydraulic system, is moved to engage with a tapered clamping ring. The clamping ring is thereby moved to engage with suitably formed grooves in the exterior of the first and second pipes, in order to draw the ends of the pipes into contact. Again, the coupling of U.S. Pat. No. 4,049,297 is applied to the exterior of the pipes being coupled and relies upon profiles formed on the outside of the pipes, resulting in an increased diameter of the pipe assembly.
A tubular connector is also disclosed in U.S. Pat. No. 4,265,470. The connector requires a shoulder on the outer surface of a first tubular member to be connected. A collet extends around the outer surface of the first tubular member and engages with the shoulder. The collet comprises a plurality of axially extending fingers, having internal ridges for engaging with corresponding ridges in the outer surface of a second tubular member. A lock ring is used to secure the fingers of the collet into engagement with the ridges in the outer surface of the second member and is retained by a lock nut threaded onto the outside of the second member. This coupling requires the tubular members being connected to be machined in order to provide the essential elements of the connector assembly.
A further coupling disclosed in U.S. Pat. No. 4,372,584 comprises a male member and a female member for connection to the outside of respective first and second pipe sections. The male member comprises a locking member having a locking sleeve comprising a plurality of bendable locking fingers extending in an axial direction from the locking sleeve. A piston is provided to displace the free ends of the locking fingers radially outwards into engagement with the female member. The free ends of the locking fingers bear against an inner surface of the female member, with the effect of drawing the ends of the two pipe sections together. The female member is shaped to allow the locking fingers to be displaced to an over center position. The coupling disclosed in U.S. Pat. No. 4,372,584 is employed on the outside of the pipes being coupled, thus adding substantially to the overall diameter of the pipe assembly. The coupling dos not utilize existing profiles on the pipes being connected, in particular profiles on the interior surface of the pipes. In addition, it would appear that, once the locking fingers having moved into the over center position, there is no means for unlocking the coupling and disconnecting the pipes.
A wellbore lock system is disclosed in U.S. Pat. No. 5,617,918. The lock system comprises a radially moveable engagement member. The engagement member is moved from a first retracted position to a second extended position by a sleeve, the engagement member engaging with a profile formed in a subsurface nipple when in the second position. A seal assembly is provided, in which a seal is expanded radially outwards by an actuation assembly in order to seal the union against fluid leaks.
There remains a need for an improved apparatus to connect tubular members, such as pipes and subsea risers. It would be advantageous if the improved apparatus would be able to be configured in an arrangement of minimal diameter. Preferably, such an apparatus would engage with pre-existing profiles on the interior surface of an existing tubular member, for example a subsea wellhead. It would be further advantageous if such an apparatus could be operated remotely, for example from the sea surface, and be releasable when desired, in order to disconnect the tubular members. Finally, it would be advantageous if the apparatus could employ existing, conventional tubular members, such as pipes, risers wellheads and the like, without any modification being necessary to provide the essential working elements of the apparatus.
Surprisingly, it has now been found that an improved apparatus for connecting two tubular members, such as pipes and risers in oilfield applications, is one in which a locking member is provided and in which the locking member is first engaged to lock the two tubular members together to prevent relative axial movement between the two, and thereafter applying a tensioning axial load to the locking member, in order to urge the end portions of the tubular members together.
According to the present invention, there is provided, in a first aspect, a connector for connecting-a first tubular member to a second tubular member, the second tubular member having a seating surface and comprising an engagable locking profile, the connector comprising:
a housing for securing the connector to the end portion of the first tubular member, the housing comprising a seating surface for contacting the seating surface of the second tubular member;
a locking assembly having a locking portion engagable with the locking profile of the second tubular member, the locking assembly movable between an unlocked position, in which the locking portion of the locking assembly is not in engagement with the locking profile of the second tubular member, to a locked position, in which the locking portion of the locking assembly is engaged with the locking portion of the second tubular member and in which the seating surface of the housing is in contact with the seating surface of the second tubular member;
a first actuator operable to move the locking assembly from the unlocked position to the locked position;
a second actuator operable after operation of the first actuator to apply an axial tensile load to the locking assembly, thereby urging the seating surface of the housing against the seating surface of the second tubular member.
The locking portion of the locking assembly preferably engages with a locking profile disposed on the inner surface of the second tubular member. In this way, the overall diameter of the connector may be kept to a minimum, providing advantages in operations involving deep draft caisson vessels and tension leg platforms. The connector may be mounted onto the end of an existing tubular member, for example a riser, by means of a conventional means, such as a flange, with little or no modification of the existing installation being required.
In a preferred arrangement, the second actuator is operable only after the locking portion of the locking assembly is fully engaged with the locking portion of the second tubular member.
In a preferred embodiment, the locking portion of the locking assembly is moved in a radial direction when acted upon by the first actuator. In this arrangement, it is advantageous to have the locking assembly comprise a groove dog for engaging with a complementary running groove in the second tubular member when the locking assembly is in the locked position.
The first actuator preferably comprises a first actuator collar movable in the axial direction, the first actuator collar comprising an actuator portion, which acts upon the locking portion of the locking assembly when the collar is moved in an axial direction. The actuator portion may comprise a taper, which is brought into contact with the locking portion of the locking assembly when the first actuator collar is moved in an axial direction. Continued movement of the first actuator collar will cause the taper to urge the locking portion of the locking assembly into engagement with the locking profile of the second tubular member.
The locking assembly preferably comprises a loading portion, distanced from the locking portion of the locking assembly in the axial direction. The loading portion is operable upon by the second actuator to apply an axial tensile load to the locking assembly. In this arrangement, the second actuator preferably comprises a second actuator collar, which may be moved in an axial direction, thereby causing an axial tensile load to be applied to the locking assembly. The connector assembly preferably comprises a loading member, such as a loading ring, which applies the axial tensile load to the locking assembly when the second actuator collar is moved in an axial direction. The loading member may be provided such that a radial movement of the loading portion of the locking assembly caused by an axial movement of the second actuator collar causes the loading member to apply the aforementioned axial tensile load to the locking assembly. This may be achieved, for example, by providing a first taper on the loading portion of the locking assembly to cooperate with and act against a corresponding second taper on the loading member. The loading member is preferably a ring disposed radially outwards of the loading portion of the locking assembly. Radial movement of the loading portion of the locking assembly is conveniently provided by providing a taper on the second actuator collar which acts against the loading portion of the locking assembly when the second actuator collar is moved in an axial direction. The connector assembly preferably comprises a gasket disposed in the housing to provide a seal between the housing and the tubular member. In a preferred arrangement, the loading member is moveable in an axial direction under the action of applying an axial tensile load to the locking assembly. This axial movement of the loading member may be used to set the gasket and provide the seal between the housing and the second tubular member.
In a preferred embodiment, the locking assembly comprises a plurality of axially extending locking members, for example locking fingers, each locking member having a locking portion at a first end and a loading portion at a second end.
As noted, the first and second actuators preferably comprise first and second actuator collars. In a preferred embodiment, the first and second actuator collars are the first and second actuator portions of a single actuator collar. Axial movement of the actuator collar causes the first actuator portion to move the locking assembly from the unlocked position to the locked position. Continued movement of the actuator collar in the axial direction causes the second actuator portion to cause an axial tensile load to be applied to the locking assembly.
The locking assembly is preferably biased into the unlocked position. This may be achieved by providing a resilient biasing member, for example a split ring disposed in a circumferential groove radially outwards of the locking assembly, the first actuator having to act to compress the split ring in the groove in order to move the locking portion of the locking assembly into engagement with the locking profile of the second tubular member.
The locking assembly is preferably moveable from the locked position to the unlocked position, in order to disconnect the first and second tubular members. In the embodiments discussed above, in which the first and second actuators comprise separate actuator collars or separate portions of a single actuator collar, it is convenient if movement of the collar or collars in one axial direction moves the locking assembly from the unlocked position to the locked position and thereafter causes an axial tensile load to be applied to the locking assembly. Movement of the collar or collars in the reverse axial direction will first release the axial tensile load being applied to the locking assembly and, thereafter, allow the locking assembly to move into the unlocked position. In a preferred arrangement, the connector assembly is provided with means, for example a hydraulic system, for applying a first force to move the locking assembly into the locked position and a second force to return the locking assembly to the unlocked position. In the interests of safety, it is preferred that the arrangement allows a greater force to be applied to move the locking assembly into the unlocked position.
The connector preferably comprises an override assembly, by which the locking assembly may be moved into the unlocked position. This may be accomplished by a remote means, for example by a remotely operated submersible vehicle in subsea locations, and is preferably independent of the primary system by which the locking assembly is moved into the locked and unlocked positions. The override system may comprise a lock for securing the locking assembly in the locked position. In a preferred embodiment, the override system comprises an indicator, visible from outside the connector assembly, to indicate the position of the locking assembly within the connector.
The connector assembly preferably comprises a centralizing ring for centrally locating the position of the first tubular member with respect to the second tubular member. The connector assembly is preferably arranged such that a couple is generated between the centralizing ring and the region of contact of the seating surface of the housing and the seating surface of the second tubular member. The couple, once formed, will resist bending moments applied to the connection when in use.
In a preferred embodiment, fluid pressure within the second tubular member, such as the downhole pressure present in a wellhead, biases the locking assembly into the locked position.
In a further aspect, the present invention provides a method of connecting a first tubular member to a second tubular member, the second tubular member having an engagable profile and a seating surface, which method comprises:
providing a connector assembly comprising a seating surface and a locking member having a locking portion;
connecting the connector assembly to an end of the first tubular member;
engaging the locking portion of the locking member with the engagable profile of the second tubular member, the locking member thereby retaining the seating surface of the connector assembly in contact with the seating surface of the second tubular member; and
thereafter applying an axial tensile load to the locking assembly to urge the seating surface of the connector assembly into contact with the seating surface of the second tubular member.
Preferably the locking assembly engages with an engagable profile disposed on the inner surface of the second tubular member. In this way, the diameter of the connector assembly may be kept to a minimum, as discussed hereinbefore.
The locking portion of the locking assembly is preferably moved in a radial direction to engage with the locking profile of the second tubular member. In the case in which the profile being engaged is on the inner surface of the second tubular member, the locking portion of the locking assembly is moved radially outwards into engagement with the locking profile, in order to lock the first and second tubular members together.
The locking assembly preferably comprises a loading portion moveable in a radial direction, whereby radial movement of the loading portion causes an axial tensile load to be applied to the locking assembly. Again, when the profile being engaged by the locking portion of the locking assembly is on the inner surface of the second tubular member, the loading portion is preferably moved in a radially outwards direction in order to apply the axial tensile load to the locking assembly.
The axial tensile load is preferably applied to the loading portion of the locking assembly by a loading member, for example a loading ring. The axial tensile load may be applied by the interaction of a first taper on the loading portion of the locking assembly and a second taper on the loading member. The loading member is preferably moved in an axial direction under the action of applying the axial tensile load to the locking assembly. In this way, the loading member may be used to set a gasket retained in the connector assembly and thereby effect a seal between the connector assembly and the second tubular member.